1. Field of the Invention
The present general inventive concept relates to an image display device, such as a projection television. More particularly, the present general inventive concept relates to an optical projection system, which has a compact depth and an image display device having the same.
2. Description of the Related Art
An image display device, such as a projection television, generates an image using a micro display, and enlarges the image via an optical projection system to project the image onto a large-sized screen. Consumer demand for the image display device having the large-sized screen has recently increased.
FIG. 1 illustrates a conventional projection television 10.
The projection television 10 comprises a lamp 1 for generating light beams, a parabolic reflector 2 for reflecting the light beams, a lighting lens 3 for compressing (i.e., condensing) the light beams, a light valve 4 for modulating light, shade, and space density of the compressed light beams according to electronic image signals and forming an image therefrom, a projecting optic lens 5 for enlarging and projecting the image, and a screen 6 for displaying the image.
The operation of the conventional projection television 10 will be briefly described with reference to FIG. 1. First, the light beams generated by the lamp 1 are reflected to the lighting lens 3 by the parabolic reflector 2, and the light beams are compressed and projected to the light valve 4.
The light valve 4 modulates the light beams radiated from the lighting lens 3 according to the electronic image signals to form the image, and the light valve 4 projects the image to the projecting optic lens 5.
The projecting optic lens 5 enlarges and projects the image onto the screen 6, and the screen 6 displays the enlarged image thereon.
In the conventional projection television 10 having the structure described above, a depth of the conventional projection television 10 depends on a distance between the parabolic reflector 2 and the screen 6. As such, a wide-angle projecting optical lens capable of projecting the image by a wide angle is used as the projecting optic lens 5 for minimizing the depth of the conventional projection television 10.
However, since the wide-angle projecting optical lens used to increase an angle of view has limitations, decreasing the depth of the conventional projection television 10 using the wide-angle projection optical lens also has limitations.
In an attempt to overcome the drawbacks described above, another projection television 10′ illustrated in FIG. 2 has been used. The projection television 10′ reflects an optical path of the projecting optic lens 5 to project the image onto the screen 6 from a vertical direction to a horizontal direction by arranging a flat reflecting mirror 7 between the projecting optic lens 5 and the screen 6 at about a 45 degree angle with respect to the vertical direction.
However, the projection television 10′ arranges a lighting system comprising the lamp 1, the parabolic reflector 2, the lighting lens 3, and the projecting optic lens 5 perpendicular to the screen 6 such that the depth of the projection television 10′ is reduced to a distance between the flat reflecting mirror 7 and the screen 6. As such, the depth decreases more than the conventional projection television 10, however, an image projected back by the flat reflecting mirror 7 may tend to interfere with the image formed by the light valve 4 and projected from the lighting system. As a result, the image gets grainy or dim.
To prevent the problems described above, a convex mirror may be used instead of the flat reflecting mirror 7 to prevent image interference. However, in this case, the image displayed on the screen 7 is distorted.